Local Structure and Li-ion Transport Mechanism in LiFSI/DME/BTFE Electrolyte Revealed by Molecular Dynamics Simulation

Fluorinated ether-based electrolytes represent a promising avenue for improving lithium-ion battery performance and safety, yet the molecular mechanisms governing ion transport in these systems remain insufficiently understood. To elucidate the solvation behavior and ion dynamics in mixed solvents, molecular dynamics simulations of 1M (bisfluorosulfonyl)imide (LiFSI) / 1,2-dimethoxyethane (DME) / bis (2,2,2-trifluoroethyl)ether (BTFE) (1:1) system were performed. The results reveal a distinct solvation preference: Li+ form predominantly anion-rich aggregates (FSI3DME1BTFE0, 28.9%) instead of traditional solvent-separated structures, with fluorinated BTFE completely excluded from the first coordination shell despite its equimolar presence. Diffusion analysis showed significant mobility differences – BTFE diffuses 17-18 times faster than ionic species−while van Hove correlation function demonstrate that Li+ transport proceeds via hopping between confined regions rather than continuous diffusion. Cluster analysis reveals small weakly charged aggregates dominating the electrolyte structure, explaining the system’s efficient charge transport. These molecular insights provide design principles for optimizing fluorinated ether electrolytes with enhanced ionic conductivity.